Organic light-emitting display device and method of driving the same

Abstract

An organic light-emitting display device includes a display unit having a plurality of pixel units. The display device also includes a timing controller for calculating a black bias pixel ratio (BBPR) of the display unit based on image signals provided by an external source and for generating a control signal based on the BBPR. The BBPR is the ratio of a number of pixel units in a black state to a total number of pixel units. A power supply unit provides a driving voltage to the display unit based on the control signal from the timing controller, wherein the power supply unit provides a first driving voltage to the display unit when the BBPR is less than a reference value and provides a second driving voltage, which is higher than the first driving voltage, otherwise.

What is claimed is: 
     
       1. An organic light-emitting display device comprising:
 a display unit comprising a plurality of pixel units; 
 a timing controller configured to calculate a black bias pixel ratio (BBPR) of the display unit based on an image signal provided by an external source and to generate a control signal based on the BBPR; and 
 a power supply unit configured to provide a driving voltage to the display unit based on the control signal provided by the timing controller, 
 wherein: 
 the BBPR is a ratio of a number of pixel units in a black state to a total number of pixel units in the display unit, and 
 the power supply unit is configured to provide a first driving voltage to the display unit when the BBPR is less than a reference value and to provide a second driving voltage to the display unit when the BBPR is greater than or equal to the reference value, wherein the second driving voltage is higher than the first driving voltage, 
 wherein a difference between the first and second driving voltages is greater than a difference between a black grayscale voltage and a white grayscale voltage. 
 
     
     
       2. The organic light-emitting display device of  claim 1 , wherein the difference between the first and second driving voltages is greater than 3.5 V. 
     
     
       3. The organic light-emitting display device of  claim 1 , wherein the reference value is 90%. 
     
     
       4. The organic light-emitting display device of  claim 3 , wherein the display unit is operated in an always-on display (AOD) mode when the BBPR is 90% or higher. 
     
     
       5. The organic light-emitting display device of  claim 1 , wherein the timing controller calculates the BBPR based on an on-pixel ratio (OPR), wherein the OPR is a ratio of a number of pixel units emitting light to the total number of pixel units in the display unit. 
     
     
       6. The organic light-emitting display device of  claim 5 , wherein the OPR is calculated for each group of pixel units emitting the same color of light, from among the plurality of pixel units. 
     
     
       7. The organic light-emitting display device of  claim 1 , wherein the power supply unit is configured to provide a first initialization voltage to the display unit when the BBPR is less than the reference value and is configured to provide a second initialization voltage to the display unit when the BBPR is greater than or equal to the reference value, wherein the second initialization voltage is higher than the first initialization voltage. 
     
     
       8. An organic light-emitting display device comprising:
 a display unit comprising a plurality of pixel units, each of the pixel units comprising an organic light-emitting diode (OLED); 
 a timing controller is configured to calculate a BBPR and set a driving mode based on the BBPR, wherein the BBPR is a ratio of a number of pixel units in a black state to a total number of pixel units in the display unit; and 
 a power supply unit is configured to provide a driving voltage corresponding to the set driving mode to the display unit, 
 wherein 
 the timing controller is configured to set a first driving mode when the BBPR is lower than 90% and to set a second driving mode when the BBPR is 90% or higher, and 
 the power supply unit is configured to provide a first driving voltage to a first electrode of the OLED of each of the pixel units when the first driving mode is set and is configured to provide a second driving voltage to the first electrode of the OLED of each of the pixel units when the second driving mode is set, wherein the second driving voltage is higher than the first driving voltage. 
 
     
     
       9. The organic light-emitting display device of  claim 8 , wherein a difference between the first and second driving voltages is greater than a difference between a black grayscale voltage and a white grayscale voltage. 
     
     
       10. The organic light-emitting display device of  claim 8 , wherein the difference between the first and second driving voltages is less than 3.5 V. 
     
     
       11. The organic light-emitting display device of  claim 8 , wherein a difference between the first and second driving voltages is greater than 3.5 V. 
     
     
       12. The organic light-emitting display device of  claim 8 , wherein each of the pixel units further comprises:
 a driving transistor comprising a first electrode electrically connected to the OLED; and 
 a compensating transistor electrically connected to the first electrode and a control electrode of the driving transistor. 
 
     
     
       13. The organic light-emitting display device of  claim 8 , wherein the timing controller is configured to calculate the BBPR based on an on-pixel ratio (OPR), wherein the OPR is a ratio of a number of pixel units emitting light to the total number of pixel units in the display unit. 
     
     
       14. The organic light-emitting display device of  claim 8 , wherein the second driving mode is an AOD mode. 
     
     
       15. The organic light-emitting display device of  claim 8 , wherein the power supply unit is configured to provide a first initialization voltage to the display unit in the first driving mode and to provide a second initialization voltage to the display unit in the second driving mode, wherein the second initialization voltage is higher than the first initialization voltage. 
     
     
       16. A method of driving an organic light-emitting display device, comprising:
 calculating a BBPR, which is a ratio of a number of pixel units in a black state to a total number of pixel units; 
 generating a control signal based on the BBPR; and 
 providing a driving voltage corresponding to the control signal to the pixel units, 
 wherein the providing the driving voltage corresponding to the control signal, comprises providing a first driving voltage to the pixel units when the BBPR is less than a reference value and providing a second driving voltage to the pixel units when the BBPR is greater than or equal to the reference value, wherein the second driving voltage is higher than the first driving voltage, 
 wherein a difference between the first and second driving voltages is greater than a difference between a black grayscale voltage and a white grayscale voltage. 
 
     
     
       17. The method of  claim 16 , wherein the reference value is 90%. 
     
     
       18. The method of  claim 16 , wherein the calculating the BBPR, comprises calculating the BBPR based on an OPR, wherein the OPR is a ratio of a number of pixel units emitting light to the total number of pixel units.